O-K and Co-L XANES Study on Oxygen Intercalation in Perovskite SrCoO3-delta
Journal
Chemistry of Materials
Journal Volume
22
Journal Issue
1
Pages
70-76
Date Issued
2010
Author(s)
Abstract
Evolution of the O-K and Co-L edge XANES spectra for SrCoO3-15 upon increasing oxygen content from 2.50 to 2.82 reveals that superoxide (O 2-) related features are overwhelmingly strong in the surface region of highly oxygen-deficient samples. Moreover, should it be always present in the bulk, octahedrally coordinated cobalt is unobservable in the surface region of highly oxygen-deficient samples. On the other hand, the surface region hosts square-pyramidally coordinated cobalt even in brownmillerite SrCoO 2.50. Observations in the present work support an oxygen-intercalation mechanism in which (i) O2 is first absorbed on the surface as O2-, (ii) then reductively split into Ox- associated with square-pyramidally coordinated cobalt, and (iii) finally in the bulk eventually reoxidized to Oz- (O < z < x) being attached to octahedrally coordinated cobalt. The fact that only minute chemical shifts of the Co-L edge branches are seen indicates that electron transfer mostly takes place between oxygen atoms. © 2009 American Chemical Society.
SDGs
Type
journal article